CVE-2026-40366
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedAccess of resource using incompatible type ('type confusion') in Microsoft Office Word allows an unauthorized attacker to execute code locally.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceType confusion vulnerability in Microsoft Office Word allows an attacker to execute arbitrary code locally through a specially crafted document. The vulnerability stems from improper type handling when Word processes certain document elements, potentially enabling memory corruption and code execution.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE dataall versions= 2019= 2021= 2024= 2016CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Local
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Verify Microsoft Word is installedCheck for WINWORD.EXE in typical installation paths (C:\Program Files\Microsoft Office\root\Office##\ or C:\Program Files (x86)\Microsoft Office\root\Office##\) or query registry key HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\WINWORD.EXEAffected if WINWORD.EXE is not found - Word is not present on the system
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Obtain the installed Word version numberRun 'winword.exe --version' from Command Prompt or PowerShell, or right-click WINWORD.EXE in the installation directory, select Properties, and view the Details tab for the Product versionAffected if The command fails or returns no version - cannot determine if Word is installed
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Identify the Office subscription or license typeCheck File > Account in Word to see if it shows Microsoft 365, or check registry HKLM\SOFTWARE\Microsoft\Office\ClickToRun\Configuration for Click-to-Run installs, or HKLM\SOFTWARE\Microsoft\Office\16.0\Word\InstallRoot for MSI installsAffected if Unable to determine the Office distribution type to map version correctly
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Compare against affected version listCross-reference the obtained version with these affected products: Microsoft 365 Apps (all versions), Microsoft Office 2019, Microsoft Office Long Term Servicing Channel 2021, Microsoft Office Long Term Servicing Channel 2024, or Microsoft Word 2016Affected if The installed version matches any of the listed affected versions or is an unspecific build of Microsoft 365 Apps
The environment is affected if Microsoft Word is installed and the installed version corresponds to Microsoft 365 Apps (any version), Office 2019, Office LTSC 2021, Office LTSC 2024, or Word 2016.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataApply Microsoft security updates for Office Word as they become available; avoid opening untrusted or unsolicited Word documents; implement email gateway filtering for potentially malicious attachments.
- Consultation2.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,096.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-40366 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-40366 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data